This invention concerns arrangements for providing air bag deployment openings in automotive interior trim structure. Inflatable cushion devices (commonly referred to as "air bags") have been devised for automotive vehicles, in which one or more air bags are stowed in respective storage spaces located within the passenger compartment. Typically a driver's side air bag is stored in a compartment in the center of the steering wheel and a passenger's side air bag is stored in a compartment behind the instrument panel. Upon detection of a relatively severe collision, the air bag or bags are very rapidly inflated to be deployed in positions to cushion the driver and/or passengers from injury-causing contact with the interior structure of the auto.
The air bags must be neatly stowed out of sight and so as to be resistant to tampering, yet able to deploy into the passenger compartment in an instant. This requires a sturdy closure panel for the deployment opening, which preferably minimizes the visual impression of the presence of the closure, and yet reliably opens when the air bag is deployed under the wide range of ambient temperature conditions for which the auto is designed for use, and over the entire useful life of the car.
Such closures are usually opened by the force exerted by the inflating air bag, and the deployment of the air bag must not be appreciably slowed by resistance to the opening of the closure. The considerable force applied by the inflating air bag must not result in fragmentation or separation of the closure, lest debris be projected towards persons in the passenger compartment.
The closure is of necessity disposed facing the interior of the passenger compartment, and thus must be aesthetically compatible with the auto interior trim.
One approach has been to completely cover a closure door substrate with a seamless expanse of decorative vinyl skin covering extending completely over the adjacent instrument panel structure and/or steering wheel cover, which covering is ruptured along the perimeter of the opening when the closure is forced open.
The vinyl covering is relatively tough and resistant to tearing.
Preweakening of the covering has been utilized to facilitate severing by cutting of a notched groove into the inside of the cover in a pattern matching the sides of the closure door. U.S. Pat. No. 5,082,310 issued on Jan. 21, 1992, for an "Arrangement for Providing an Air Bag Deployment Opening" describes a method for cutting a groove on the inside of the vinyl skin covering.
Leather is also used as a decorative covering layer for automotive interiors. Leather is not sufficiently preweakened by scoring on the inside since it is tanned to a soft, flexible state and thus not by its nature notch sensitive.
Accordingly, the object of the present invention is to provide a method and treatment for preweakening a leather covering layer so as to be readily severed along a predetermined perimeter line as the door is forced open by the deploying air bag.